EEVEE 2.8 : the light goes through the egdes of a simple cube?
Welcome Patrick!

Yes, there are a couple of ways to handle these problems in EEVEE.

Thicker geometry reduces the problem:



Increasing the Shadow Exponent value on the spotlight makes the fade shorter.



Adding contact shadows fills in the fade:



It should however be noted that Contact Shadows are created with the depth map and may create undesired artefacts. This could be handled in a single shot but if you render a sequence it might be harder.

The VSM shadows (In render settings) generates a bit noisier shadow gradient but should be hided with less geometry.



Or if you absolutely need to keep your geometry paper thin you could add a tiny contact shadow.



Here is where you find the settings: